Why H₂-Methanol?
Silicon Fire methanol and Silicon Fire Silicon:
Spearheads of a new renewable energy industry
Prof. Dr.-Ing. Roland Meyer-Pittroff,
Technical University Munich
1. Availability and storage of energy
Our most important sources of energy are the fossil fuels coal, oil and gas, refuse and waste, renewable energy, above all hydroelectric power, biomass, wind and solar, and – as far as this is accepted – nuclear energy. In spite of great support for renewable energy over decades, in Germany in 2010 fossil fuels still accounted for 78% of the primary energy requirement (renewable energy 9.4%), and this circumstance gives rise to concerns with regard to the security of supplies because of dependence on import, as well as with regard to effects on the environment, in particular because of the greenhouse gas effect caused by carbon dioxide released during burning.
Wind and solar energy are the great new hopes for the future. The main problem with using energy from these sources is its discontinuous incidence, because, as with all demands, with the energy demand as well it is important to have the necessary amount available when it is required, and not sometime or other.
The decisive problem is storing the energy! While storing different types of energy (e.g. heat, movement, electric energy) is possible in principle with various methods (e.g. heat accumulators, flywheel energy storage devices, battery storage), this is very expensive and therefore unrealistic in practice and economically for large amounts of energy. Exceptions to this are storing potential energy (pumped-storage power plants) and chemical bond energy.
Chemical reactions usually run with the absorption or delivery of energy. Through an appropriate series connection of suitable energy absorbing and energy delivering reactions, the greatest volumes of energy can be stored in relation to the volume or mass of materials, if we disregard nuclear energy. All our fossil fuels contain solar energy that was chemically stored over millions of year and is released again by being burnt.
The good old lead accumulator, which is found in our motor vehicles as an electric battery, still has the best price-performance ratio as an electric storage system for most applications, but in relation to its mass stores only about four hundredths of the energy that is released as heat when petrol or mineral oil is combusted.
Energy storage is the main problem of wind and solar energy storage! The global state of the art at present for using this technology on a large scale is conversion into electrical energy and feeding it into the existing electrical grid. However, generation and consumption have to be in exact balance at all times in the electricity grid, so that the line frequency remains constant within the very low prescribed tolerance (0.4%). This means that for each wind and solar power installation that may fail at any time, there has to be an equally large reserve and regulating capacity in the grid, which up to now has consisted basically of thermal power plants with steam and gas turbines whose output can be adjusted accordingly. The consequence is that up to now wind and solar power installations are hardly in a position to replace thermal power plants, but merely save fuel there.
With an increasing share of wind and solar power installations in the grid the problems of securing network stability increase considerably, so that at present there is a very serious discussion concerning the necessity of new powerful pumped-storage power plants and additional power lines covering the whole of Europe and designed for very high transmission outputs, with which wind, solar and pump storage power, but also conventionally generated electricity as well, can be distributed throughout Europe, thus stabilising the grid.
Of course, questions arise concerning the feasibility and economic efficiency of such enormous storage and transmission installations, the likes of which have never existed and never been required before.
In consequence, the question must be asked emphatically whether there are not much better, more economic and ecologically more sensible facilities for using wind and solar energy than squeezing them into the corset of the electrical grid, as propagated and practised up to now, with the enormous problems and costs associated with this.
Starting from the assumption that in the distant future as well previous sources of energy, including fossil fuels, will contribute to covering energy requirements, even though the proportions will be greatly changed, to generate electricity for the electrical grid, which has to follow consumption fluctuations exactly at all times, in the first place available energy sources should be used that enable a simple needs-based regulation of generation and where possible local generation near the point of consumption with low transmission losses and costs, whereby in the case of thermal power plants waste heat utilisation in the form of rational cogeneration is to be aimed for. These energy sources are hydroelectric power, but above all fuels: fossil, biogenic and – as far as this is accepted – nuclear as well.
The use of intermittent wind and solar energy should be predestined for those applications in which discontinuity plays a subordinate role, and these are in particular conversions into chemically bound energy in the form of combustibles and fuels that are easy to store and transport, as well as chemical raw materials or new metallic energy sources such as silicon.
In Germany, for example, annual consumption of petrol is 20mn tonnes, and 30mn tonnes for diesel. This means that these fuels for automotive drives have a share of approx. 16% of the total German primary energy requirement, whose substitution with renewable energy is certainly a rewarding goal as well!
2. Silicon-Fire methanol as a renewable, climate-neutral and storable fuel
The new fuel is to be renewable and climate-neutral, be easy to store and handle as a liquid, have good fuel properties, and provide economic and ecological benefits as against bioethanol and biodiesel, which are regarded today as renewable.
As the simplest alcohol CH3OH (“wood spirit”, “first run” in alcohol distillation), the natural substance methanol fulfils all these properties; it has already proven its worth up to now as fuel for high stressed model and vehicle engines, and as a petrol additive. Since 1923, this synthesis from synthesis gases of fossil origins has been the industrial state of the art (annual global production today: approx. 45mn tonnes).
The disadvantage of methanol is that the calorific value in relation to volume is only half that of petrol; advantages are greater anti-knock properties (octane number RON = 105 as against 95 for super petrol) and greater inner engine cooling, which means that considerably higher engine performance and efficiency are possible.
The idea of introducing methanol as engine fuel on a large scale is not new. Major government programmes for fossil methanol in the USA and Germany in the 1980s and 1990s were unsuccessful because of rejection by the automotive and mineral oil industries. Methanol fuel was given a new lease of life by, among other things, the book “Beyond Oil and Gas: The Methanol Economy” by the Nobel prize-winner George A. Olah in 2006, and developments by the Swiss company Silicon Fire AG.
In recent years, using familiar technologies as a basis Silicon Fire AG has developed new process combinations, some of which have been registered for patents, that bring renewable Silicon-Fire methanol essential competitive advantages in comparison with other fuels that are regarded as renewable.
The energy supplier for Silicon-Fire methanol is renewably manufactured hydrogen H₂, that, in accordance with the state of the art, has been manufactured up to now with the help of renewable electrical energy through water electrolysis:
H2O -286 kJ/mol = H2 + 0,5O2 (Reaction 1).
The carbon for the synthesis of the methanol is not provided by fossil fuels, as in production up to now, but by carbon dioxide, CO2, which is acquired from concentrated industrial sources (e.g. waste gases from chemical processes or large furnaces, lime kilns, CO2 capture from natural gas) that otherwise emit the CO2 into the atmosphere. Later, it will be technically possible to wash CO2 out of the atmosphere, which increasingly contains it (at present 385 ppm (0.0385 % vol.)).
This means that Silicon-Fire methanol is renewable and CO2-neutral. The synthesis to methanol takes place catalytically in reactors following previous methanol production, e.g. as low-pressure synthesis at 80 bar and 265 °C:
3H2 + CO2 = CH3OH + H2O –49.6 kJ/mol.
Silicon Fire AG has developed a suitable mobile demonstration installation with a production capacity of 50 l/d and has used it successfully in trials since autumn 2010. A Silicon Fire mobile station with a capacity of 1000 l/d was planned on this basis and will be available shortly. Pro-project planning of large-scale industrial systems with capacities of 3000-5000 t/d has been concluded.
Production costs of Silicon Fire methanol can be reduced drastically if the demand for a 100% renewable origin is abandoned, which is far from achieved by competing biofuels as well.
EU Directives demand renewable energy shares in the transport sector of 10% by 2020, but at the same time (valid until the end of 2016) provide for a potential reduction in greenhouse gases for these renewable shares of (only) 35% in comparison with fossil fuels.
This results in the possibility of combining the synthesis of renewable methanol described above with traditional methanol synthesis from fossil synthesis gas, which can be carried out particularly advantageously by integrating the oxygen released in the water electrolysis for the production of hydrogen into the synthesis gas generation (for partial oxidation or for autothermal reforming of the fossil fuel). Combined in this way, costs for Silicon Fire methanol result in large-scale installations (3000 to 5000 t/d) that are considerably less than the prices for bioethanol and biodiesel.
In order to meet the EU’s demand for a 10% share of renewables in petrol within the EU by adding Silicon Fire methanol, approx. 26 million tonnes of the latter would be required, or 16 large-scale installations each with a daily capacity of 5000 t.
3. Silicon as a metal energy store
Transporting electrical energy over distances of several thousand kilometres with the available high-voltage direct current transmission is bound up with very high costs and losses. One possibility for transporting energy that is more favourable in many cases is the electrochemical reduction of a metal oxide to a pure metal at the electricity generation location, transporting the metal to the location of the energy requirement, and extracting the energy there by re-oxidation of the metal to the initial oxide e.g. for the production of hydrogen as energy carrier.
Metals such as aluminium, and in particular silicon, are suitable for this energy transport.
These metals require a large amount of specific energy for oxide reduction, which is then released again on the metal oxidation. In addition, they have the advantage that they are non-toxic and that their surfaces are protected by a passivating oxide layer, so that handling and transport the metals is not dangerous.
Silicon has the particular advantage that there are no limits to its availability as a raw material. Silicon oxide SiO2 is quartz (sand); 25.8 % by mass of the earth’s crust consists of silicon in the form of silicates or quartz.
A large part of globally traded silicon metal is already produced renewably through reduction of quartz sand in arc furnaces with charcoal, whereby the charcoal frequently comes from sustainable forestry and the electrical energy from hydroelectric power.
For the synthesis of Silicon Fire methanol the required hydrogen can be produced advantageously through the reduction of water H2O with the help of silicon Si in accordance with the total formula:
Si + 2H2O = SiO2 +2H2 -339,5 kJ/mol (Reaction 2),
whereby, along with hydrogen, quartz (sand) occurs again as product.
If the reaction heat in reaction 2 above and the calorific value of the hydrogen that is produced are added to the input silicon as energy content, at 29 MJ/kg the mass-related energy content of the silicon is roughly the same as that of coal.
Because of the passivating oxide layer, reaction 2 does not run directly but only after separation of the oxide layer, e.g. with a lye. As long ago as WW1, mobile Schuckert and Silicol plants were used to produce hydrogen for captive balloons in the field in which oxidation of the silicon to SiO2 and reduction of the water to H2 was carried out with the help of aqueous sodium hydroxide, NaOH, via sodium silicates as intermediate products.
Silicon Fire AG has developed and planned a Silicon Fire hydrogen system on the basis of known chemical reactions that works with metallic silicon or ferrosilicon and a 25% sodium hydroxide solution, in which hydrogen and quartz (sand) are produced as end products via the formation of sodium silicates, and the lye can be reclaimed. Approx. 7.6 kg silicon are required here to produce 1 kg hydrogen.
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